Electrically driven potter's wheels are known which are provided with a driving unit consisting of an electric motor and a conical roller directly coupled to the electric motor. In one known type a rim wheel on the table shaft is driven directly by the roller of the driving unit, and in another known type a belt is hung between a pulley on the table shaft and a pulley driven by the driving unit so that the speed is also reduced by the pulley-driving-part. The former will be called "direct driving type" and the latter will be called "belt driving type" or "reduction-driving type". They both have merits and disadvantages as follows:
(1) Directing Driving Type: PA0 (2) Belt Driving Type (Reduction Driving Type):
In this type the rim wheel on the shaft of the molding table is driven by a roller which is directly coupled with an electric motor. That driving unit comprising the roller and the electric motor is moved in a horizontal direction to vary the speed of the molding table. Since the speed is not reduced by a belt-and-pulley-device, the roller of the driving unit must drive the rim wheel on the molding table under a relatively large contact pressure. Therefore, the wear and fatigue of the rubber ring on the rim wheel are so large as to shorten the life of the potter's wheel. On the other hand, the structure of this potter's wheel is remarkably simplified, and further, the overall size of the potter's wheel becomes small, taking-on a compact construction.
Since the speed is reduced by the belt-and-pulley-device, the roller of the driving unit can drive the follower wheel under a relatively small contact pressure. Therefore, the wear of the rubber ring on the follower wheel is small and the life of the potter's wheel is long. But, on the other hand, the construction is comparatively complicated, the number of component parts is large and the lengthwise dimension is large. Further, this type of potter's wheel often causes noise and vibration due to an irregular wear of the belt.
Although each of the above-two types of electrically driven potter's wheels are known, in most cases potter's wheels of the belt driving type are used since the life of this type is longer than that of the direct-driving type.
One object of the present invention is to provide an electrically driven potter's wheel of the direct driving type of simple construction, small size and low price which is not accompanied with the disadvantage of short life.